But OpenGL ES 3.0 is already here (on bigger number of devices then iDevieces combined!). OpenGL ES 3.1 is behind the hill top (but we will have to see if any updates to current drivers land.. As to date I can not find any updates on Khronos conformance list. :| )
So its not so gloomy for OpenGL ES 3.0/3.1 especially for apps that will benefit (anything but simple 2D over 3D).
That being said, hardcore gaming on ibm pc clones is still big business (and it can benefit from consoles, more then ever).
So Mantle/DX12/OpenGL "AZDO" are important here. (OpenGL "AZDO" -> OpenGL 4.2 + extensions, or any driver that currently support OpenGL 4.4, so its AVAILABLE RIGHT NOW)
Biggest show stopper for OGL AZDO is OSX (if writing OpenGL code then OSX is important target most of the time). Apple need to step up their game... which they may not want to, as Metal 2.0 would suite them better (but that would also "release" Linux/Windows OpenGL from reliance on Apple whim).
And Mantle and DX12 share many basic concepts. So if game engines are being designed for it, they will work well with DX12 when its available, because all system-wide decisions will be made beforehand.